Sounds complex, but rather easy to pull off with the right conditions. Begin a Career session on any world you prefer, but I suggest Highlands (or Desert if you have Career+ unlocked).
Play through a few tracks and make sure to pull off tricks and slides with the right thumbstick to score rep. The goal is to unlock a couple crew members that give you perks to make the trick much easier to complete.
You unlock a crew member at 1,000 rep and another at 4,000 rep which is easy to rack up in one or two levels. You get a choice between four random perks, so if you don't get good perks, just end the session and give it another go. The crew member perks you want are:
Once you get the crew member perks, choose a track with a high stunt and steepness rating. Next, ride through the track until you find a suitable ramp (or hill off of the track) to get enough air to pull off the 720 backflip. As soon as you take off of a jump, hold back and either to the right or left on the right thumbstick. In relation to a compass, hold the control stick to SW or SE. Once you do the flips and spins, level out your bike and land as best you can.
May take a few attempts, but using my guidelines should make it no sweat.